1. Field of the Invention
The present invention relates to a power supply device, and in particular to a power supply device capable of supplying high DC voltages of positive and negative polarities.
In case of effecting positive and negative image development in a microfilming apparatus, an electronic copying apparatus, a laser beam printer or the like, there are required positive and negative high DC voltages for electrostatic charging.
A conventional power supply device employed for such application has separate power supply circuits for positive and negative voltages, which are suitably switched, for example, with a relay.
Due to the presence of two separate circuits, such a conventional power supply device involves a large number of component parts and is therefore inevitably large. Also, the switching of high output voltages in such conventional device gives rise to significant noise generation.